Assessment of a Fusion Polyprotein Based on HspX and Other Eight Antigen Segments for Tuberculosis Serodiagnosis

Abstract

Background: The lack of suitable diagnostic tools has paved the cornerstone for controlling and treatment of tuberculosis. Serological tests, based on multiple target antigens, represent an attractive option for its rapidity, convenience, and low-cost. Methods: Measures, including blocking antibodies against common bacteria in serum samples and synthesizing polypeptides covering un-conserved dominant B-cell epitopes of antigens, were attempted to reduce nonspecific reactions and thus improved the specificity. Meanwhile, a fusion polyprotein containing HspX and other eight antigen segments was constructed and expressed to increase the whole sensitivity. Results: The addition of only E. coli lysate partly increased the specificities. Another, peptides containing un-conserved fragments of TB antigens as well as dominant B-cell epitopes were synthesized and used to effectively reduce non-specific reactions without dramatically decreasing their sensitivities. Meanwhile, a polyprotein fusing HspX and other eight antigen segments was constructed and the sensitivity of the polyprotein was 60.2%, which was higher that of HspX and other individual antigen segments. Importantly, the specificity of the polyprotein was 93.6%, which was not significantly decreased. Conclusions: Our results demonstrate the roles of fusion polyproteins in the humoral immunity against TB infection and provide a potential novel approach for TB diagnostic development.